1. Field of the Invention
The invention relates to a probe guide duct device or apparatus for nuclear reactors and is particularly suitable for temperature measuring probes in a pressurized water reactor (PWR), such as thermocouples.
More generally, the invention is suitable for every type of removable probe and is adaptable to every type of nuclear reactor comprising a pressure resistant vessel containing a coolant, a removable cover for said vessel, a core including fuel aassemblies, and having an upper plate and upper internal equipment fast with said plate and located between said core and said cover.
2. Prior Art
Different devices are already known. They comprise guide ducts or tubes passing through the reactor cover and extending down to the level of the top of the assemblies.
French Pat. No. 2,065,512, concerning a device for the instrumentation of a core of a pressurized water reactor, describes an arrangement in which guide ducts are provided for ball probes or stationary measurement probes around the periphery of a reactor cover. They are split horizontally above the internal equipments on support arms before extending down to the level of the core.
This solution has drawbacks. The guide ducts pass through the main flow without any particular protection against shocks or turbulence. The number of ducts is limited due to the density of the upper internal equipments, and the space already required by some of these equipments such as the guide tubes for the control clusters of the reactor.
However, such a device might seem sufficient to a man skilled in the art although certain measurements points such as temperature measurement points of the coolant at the outlet of the core, are not numerous.